The present invention relates to a method for determining a machining method in a numerical control information generating apparatus.
In a numerical control machining tool, information for numerical control information generating apparatus which inputs machining data on an interactive basis and prepares numerical control information for the purpose of simplifying the generation of numerical control information is widely used. With such numerical control information generating apparatus, inputting the quality and shape of the material and the machining methods (areas to be machined, cutting direction, cutting tool, cutting conditions, sequence of machining, etc.) enables numerical control information for machining to be generated. In recent years, there has appeared a numerical control information generating apparatus which determines the machining method automatically and which generates the numerical control information through the input of the shape of the material and of the parts.
FIG. 1 showns one example of the shape of a material and of the parts. In the above-mentioned numerical control information generating apparatus which determines machining methods automatically, machining methods for a recessed shape (hereinafter referred to as "a recess") for which downward cutting is required can be determined, as shown in FIG. 1. Here, the recess includes the shape of areas E.sub.1 to E.sub.6 shown in FIG. 2. Areas E.sub.1, E.sub.4, E.sub.5, and E.sub.6 are longitudinal recesses and areas E.sub.2, E.sub.3, E.sub.6 and E.sub.7 are end surface recesses.
Next, a process in which the numerical control information generating apparatus of the prior art determines machining methods for a recess will be explained with reference to FIG. 4.
When the shape of a material and of the parts as shown in FIG. 1 are input, a machining area R.sub.0 formed by a figure element list (l.sub.3, l.sub.4, l.sub.5, l.sub.w1) is determined by comparing the two shapes (Step S100). Then, since this machining area R.sub.0 belongs to an outer circumference, its cutting direction is determined to be ".rarw." (Step S101). Of the machining area R.sub.0, a determination is made as to whether or not a downward cut is needed by comparing a figure element list (l.sub.3, l.sub.4, l.sub.5, l.sub.w1) forming the shape of parts and a cutting direction ".rarw.". If a downward cut is needed, it is determined to be a longitudinal recess (Step S102). In the example of FIG. 1, because a figure element l.sub.3 exists, it is determined to be a longitudinal recess.
Next, the cutting tool is determined by the cutting direction determined in the above and by the fact that it is a longitudinal recess (Step S103). For example, a tool as shown in FIG. 5A is determined. After comparing the angle .alpha. formed by the downward shape (l.sub.3 in FIG. 1) of the longitudinal recess and the Z-axis with the .beta. (hereinafter referred to as "a sub-cutting blade angle") formed by the sub-cutting blade of the tool and the Z-axis, a check is made to see whether or not the edge of a tool blade interferes while machining a downward shape is being machined (Step S105). If .alpha.&gt;.beta., the edge of the tool blade is not interfered with and by using the tool, a downward shape can be machined. When .alpha..gtoreq..beta. in the case of .alpha. of FIG. 1 and .beta. of FIG. 5A, a downward shape (figure element l.sub.3 in FIG. 1) cannot be machined. In such a case, as shown in FIG. 3, the figure element l.sub.3 passing the start point A of the figure element l.sub.3 and making an angle greater .beta. with respect to the Z-axis is generated. Further, a figure element l.sub.4 is divided into figure element l.sub.4 ' and l.sub.4 " at the termination .beta. of a figure element l.sub.3, and the machining area R.sub.0 is divided into a machining area R.sub.1 formed by a figure element list (l.sub.3, l.sub.4 ", l.sub.5, l.sub.w1) and a machining area R.sub.2 formed by a figure element (l.sub.3, l.sub.4 ', l.sub.s) (Step S106). A cutting direction ".fwdarw." is determined for the machining area R.sub.2 divided in this way (Step S107) and the tool as shown in FIG. 5B is selected (Step S108). Cutting conditions and the sequence of machining are determined (Steps S109 and S110), completing the determination of the machining methods or modes.
When the part is determined to be not a longitudinal recess in the Step S102 of the flowchart of FIG. 4, a tool is determined by the cutting direction (Step S104) and control jumps to the Step S109. Machining modes for the end surface recess are determined in similar processes.
In the determination method of the prior art as mentioned above, machining modes for machining a recess like areas E.sub.1 to E.sub.8 shown in FIG. 2 can be determined automatically. However, for a shape in which a longitudinal recess and an end surface recess overlap, machining modes cannot be determined automatically. Therefore, to prepare numerical control information used for machining such shapes, the operator must specify a machining area, a cutting direction, a cutting tool and the sequence of machining one by one. For a shape as shown in FIG. 8, efforts to input the above-mentioned data are great because the machining methods are complex, and therefore a great burden is placed on the operator.
That is, in the numerical control information generating apparatus of the prior art, for a simple recessed shape, machining methods can be determined automatically by checking the interference of the edge of the tool blade. However, for a complex shape in which recessed shapes overlap, the machining methods cannot be determined automatically. When the operator machines a shape as shown in FIG. 8, inputting the machining methods manually is required. Therefore a great deal of efforts are spent on the input.